Michael A Lang and Charles E Lehner, convenors of the RDP Workshop, published a response to these findings in a March 2006 issue of Diving and Hyperbaric Medicine. They report that the experimental data presented by Edmonds et al fails to provide sufficient evidence for overturning the Workshop’s conclusions, and present a case outlining the flaws in their study.

Lang and Lerner state that Edmonds and team have failed to contribute any significant new data, missed significant points made during the workshop, and in an especially damning assertion, wonder if the authors had purposefully inserted bias by designing an experiment that would support their preconceptions. Lang and Lerner also state that extrapolating data gathered from guinea–pig experiments to humans is inappropriate, and in fact represents the greatest weakness of their argument.

They also point out that Edmonds et al chose to ignore the same historical data the Workshop reviewed (military, commercial, and scientific diving records gathered over 50 years) in making their recommendations about RDPs.
This historical data, as well as chamber operations showing that most divers treated dived FDPs, contributed to the recommendations made by the Workshop. In fact, neither the US Navy nor commercial diving prohibits RDPs. A review of AAUS standards reveals that neither do they.

The assertion by Edmonds et al that Huggins’ chamber observations support a ban against RDPs is flawed, according to Lang and Lehner, because not only was the data statistically insignificant , but no controls were placed on DCS risk factors (dive profile, maximum dive depth, etc.).

Lang and Lehner also take Edmonds et al to task for misinterpreting the Workshop’s findings with regard to nitrogen loads, and instead, erroneously testing “mirror” profiles. Contrary to what they say Edmonds et al assumes, the Workshop concluded that FDPs and RDPs do not require comparable decompression times. The model presented at the Workshop emphasizes that no matter the dive profile, quality decompression according to the last dive, and prevention of bubble creation at an early stage (and subsequent remedy of if created), must be adhered to. As an example, they explain that a bubble model of decompression proscribes much longer surface intervals after first and second dives in order to provide comparable DCS risks for FDPs and RDPs. Consider this forward dive profile: 30 meters salt water (msw)/30 min, 15 min surface interval (SI); 20 msw/30 min, 15 min SI; 10 msw/30 min. To approximate equal DCS risks for a reverse order dive profile, surface intervals would have to be significantly increased: 10 msw/30 min, 90 min SI; 20 msw/30 min, 120 min SI. This significant increase in surface interval times underscores the practical reasons for not performing reverse dive profiles.

Despite the arguably faulty science conducted by Edmonds et al, both groups agree that reverse profiles are not mirror images of forward profiles, and require entirely different decompression obligations. However, Edmonds et al advise against them, and the Workshop concludes that there is no reason to prohibit them for no-deco dives less that 130 fsw and depth differentials less than 40 fsw. I would also like to emphasize that substantially longer surface intervals are required for RDPs.

References:
Lang MA, Lehner CE. Smithsonian Institution, Washington DC, USA, Dir. Smithsonian Marine Science Network and Scientific Diving Program; University of Wisconsin, Madison, Wisconsin, USA, Assis. Scientist and Dir. Blotron Diving Physiology Laboratory. Reverse dive profiles: the making of a myth. A response. Diving and Hyperbaric Medicince 2006; 36:51-5.